12-week training program (24-36 one-hour sessions) at 70-85% of their maximal heart rate (HR). In the CT group training is supervised by a physical therapist; in the HT group training is performed in the home environment using a HR monitor to determine training intensity and with weekly feedback / motivation by an exercise specialist who has access to the online HR-data. After 12 weeks, subjects in the HT group are encouraged to continue using the HR monitor.